Heating device for passage through subterranean asphalt and method of use

ABSTRACT

A lowermost casing segment in a tubular casing string, capped with a cast iron end cap, has an ignitable thermite mixture within the interior of such casing segment which, when ignited, superheats the end cap and the casing segment, to allow the casing segment and the end cap to be lowered completely through a subterranean asphalt formation without allowing the asphalt to enter the interior of the casing segment. The cast iron end cap is then drilled out to allow further drilling through the casing segment into oil and gas formations beneath the asphalt formation. In a first embodiment, the casing segment has a top cap to constrain the thermite mixture. In a second embodiment, the thermite mixture is located within a metal capsule which can be lowered into the casing segment to rest against the bottom end cap, and then be removed by a wireline.

TECHNICAL FIELD

The present invention relates generally to systems and methods used for creating passages through subterranean asphalt.

BACKGROUND OF THE INVENTION

The use of drilling equipment to discovery and recover oil has been in place for centuries. Recent drilling improvement have lead to drilling for hydrocarbons in a variety of areas that were previously not thought possible. It has been recently discovered that deposits of hydrocarbons may exist under certain patches of naturally occurring subterranean asphalt. One of the problems associated with drilling through asphalt is the gummy, tarry nature of asphalt gumming up drill casing and closing boreholes. In several embodiments the present inventive device addresses the issue of removing asphaltic borehole clogs and laying casing through the asphaltic layers without gumming up the casing with asphalt.

Several other unique attributes of the inventive device will be illustrated in the detailed description sections.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a side view of a typical borehole through asphalt with the asphalt formation closing the borehole.

FIG. 2 illustrates a side view of a borehole with one embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in inactive mode.

FIG. 3 illustrates a side view of a borehole with one embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in an active mode.

FIG. 4 illustrates a side view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in active mode.

FIG. 5 illustrates a side view of a borehole with a thermite mixture encapsulated in a cast iron capped segment of casing in active mode positioned to extend past an asphaltic layer.

FIG. 6 illustrates a side view of a borehole with a drill pipe and bit run through the caps and thermite slag.

FIG. 7 illustrates a side view of a borehole with a cement plug and a wiper plug inside the casing.

FIG. 8 illustrates a side view of a borehole with the remaining thermite slag and cement drilled out.

FIG. 9 illustrates a side view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a capsule in active mode being ignited from the top down.

FIG. 10 illustrates a side view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a capsule in active mode being ignited from the bottom up.

FIG. 11 illustrates a side view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in active mode positioned to extend past an asphaltic layer.

FIG. 12 illustrates a side view of a borehole with the capsule removed.

FIG. 13 illustrates a one type of geographic strata in which the inventive device could be utilized.

The above mentioned and other objects and advantages of the present apparatus, and a better understanding of the principles and details of the present apparatus, will be evident from the following description taken in conjunction with the appended drawings.

The drawings constitute a part of this specification and include exemplary embodiments of the present apparatus, which may be embodied in various forms. It is to be understood that in some instances, various aspects of the apparatus may be shown exaggerated, reduced or enlarged, or otherwise distorted to facilitate an understanding of the present apparatus.

For a further understanding of the nature and objects of the present apparatus, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers.

DETAILED DESCRIPTION OF DRAWINGS AND PREFERRED MODES FOR CARRYING OUT THE INVENTION

For a further understanding of the nature, function, and objects of the present apparatus, reference should now be made to the following detailed description taken in conjunction with the accompanying drawings. Detailed descriptions of the embodiments are provided herein, as well as, a mode of carrying out and employing embodiments of the present apparatus. It is to be understood, however, that the present apparatus may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present apparatus in virtually any appropriately detailed system, structure, or manner. The practice of the present apparatus is illustrated by the following examples which are deemed illustrative of both the process taught by the present apparatus and of the product and article of manufacture made in accordance with the present apparatus. It should be noted that throughout this application the term “asphalt” is meant to include a dark brown to black cementitious material in which the predominant constituents are bitumens that occur in nature or are obtained in petroleum processing. “Asphalt” may also include bitumens, which is a generic term for natural or manufactured black or dark-colored solid, semisolid, or viscous cementitious materials that are composed mainly of high molecular weight hydrocarbons. The term “asphalt” as used in this application also includes any tars and pitches derived from coal.

In drilling for oil and gas, the drill string is typically made up with a plurality of tubular drill pipe joints threaded together and having a drill bit at its lower end. As is well known, as the upper end of the drill string is rotated at the earth's surface, usually with a rotary table, the rotating drill string causes the drill bit to rotate and to thus drill deeper and deeper.

If the drill pipe and drill bit encounter an asphalt formation, the drill bit drills right through the formation, allowing the drill bit and tubular drill string to pass right on through the asphalt formation. However, when the drill bit and drill string are removed, for whatever the reason, such as for example, to replace a dulled or damaged drill bit, or to run in a series of steel casing joints to line the borehole, the borehole remains substantially intact in the rock and/or sand formation above the asphalt, and in the sand and/or rock formation below the asphalt, but the plastic asphalt formation “closes” the borehole. When one attempts to run the steel casing into that section of the borehole, the casing string is impeded by the plastic asphalt, typically warmed up and at least partially liquified because of the depth of the asphalt formation surrounding the borehole. When the asphalt is not warmed up enough to liquify, the casing merely stops because of the capped lower end being unable to penetrate the still solid asphalt. If the lower end is open, i.e., uncapped, the presence of the asphalt within the interior of the casing is highly undesirable.

Such asphalt formations are oftentimes not encountered above oil and gas formations, but in many cases, when existing, are found at depths of some 3,000 to 5,000 feet below the mud or ground line. At other times, asphalt is found at more shallow depths, for example, when drilling in river beds, such as the settled tar pits existing beneath the silt formations underneath the river beds. However, in all such cases, regardless of the depths at which the asphalt formation is encountered, it is highly desirable to prevent the asphalt from entering into the interior of the steel casing liner or impeding the interior of the casing and thus adversely effecting the drilling and completion operations involved in producing oil and gas from underneath said asphalt formations.

Referring now to the drawings in more detail, FIG. 1 illustrates a side, elevated view of a typical borehole through asphalt with the asphalt formation closing the borehole. The general formation 1 can be generally described as an upper area of rock or silt 2, a medial level of asphalt or asphalt composite 3 and a lower level of sand or rock 4. When drilling for oil the drill bit and drill sting will drill through the rock layer 2, the asphalt layer 3 and into the sand layer 4 which lies above the hydrocarbon layer which is the preferably desired target of the drilling. After the drill pipe is removed, but prior to inserting the casing, the bore hole 5 will still remain in the rock 2 and in the sand 4. However, the plastic asphalt layer 3 flows into the borehole 5 in its area 6. The asphalt layer 3 will oftentimes also run into the borehole in the sand 4, illustrated and identified by the numeral 7, and begin to clog that portion of the borehole. So after removal of the bit and drill string the asphalt layer 3 effectively closes the borehole 5 with an asphalt barrier 6. In order to obtain the hydrocarbons located below the sand strata 4 the asphalt layer 3 needs to be penetrated and sealed off in an efficient and productive manner.

FIG. 2 illustrates a side, elevated view of a borehole with one embodiment of a thermite mixture encapsulated in a capped segment of steel casing in an inactive mode. Thermite is a publicly available mixture of a metal oxide, for example, ferric oxide and powdered aluminum. On ignition by a ribbon of magnesium, the reaction can produce a temperature of about 2200° C. The generated heat is then transmitted by heat conduction to the casing and then to the asphalt layer. Such oxide/metal reactions provide their own oxygen supply, and thus are more dependable in a downhole environment.

The grind of the aluminum determines the speed of burning of the thermite mixture. When ground very finely, such as with flour, the thermite mixture burns very fast. The thermite mixture burns more slowly as the grind creates larger size particles. Thus, with a given grind of the aluminum, the time of the burn is dependent upon the length of the column of thermite. In a typical job, the thermite may burn at the rate of one foot per five minutes of burn. If the asphalt layer is 100′ thick, a column of thermite 20′ long will take approximately 100 minutes to burn the entire column, such as the column 13 illustrated in FIG. 2. The cap 9 and casing will move through the asphalt layer at approximately the same rate as the rate of burning, causing the cap 9 to go completely through the asphalt layer in the same 100 minutes. These are merely illustrative numbers, since the rate of burning and the extent of asphalt will vary almost with every job.

Lower casing segment 8 is lowered into the borehole 5 such that the bottom end of the lower casing segment (joint) 8 is preferably in contact with the uppermost portion of the asphalt formation layer 3. The contact portion of the lower casing segment 8 is preferably a lower dome 9 composed of preferably, but not limited to, a drillable cast iron. The cast iron dome or cap 9 is preferably engaged with the lower casing segment 8 such that there is a substantially tight seal between the two so that no solids, liquids or gases can escape into or out of the lower casing segment 8 through the cast iron dome or cap 9. The dome or cap 9 is also preferably constructed to withstand extremely high temperatures without cracking, corroding or becoming otherwise compromised. Located substantially opposite of the dome or cap 9, but still connected within the lower casing assembly 8 is another dome or cap 10. The dome or cap 9 and the dome or cap 10 are substantially aligned so as to create a hollow, interior chamber 12 within the lower casing assembly 8 which is substantially defined by the interior walls of lower casing assembly 8, the dome or cap 9 and the dome or cap 10. The dome or cap 10 is also preferably constructed of drillable cast iron to withstand extremely high temperatures without cracking, corroding or becoming otherwise compromised. The cast iron dome or cap 10 is preferably engaged with the lower casing segment 8 such that there is substantially tight seal between the two; however dome or cap 10 is preferably constructed so that there is an exhaust valve 11 running from the exterior of dome or cap 10 through dome or cap 10 and into the interior chamber 12. The exhaust valve 11 is constructed to allow for any gases existing or generated in the interior chamber 12 to escape from the interior chamber 12. The interior chamber 12 is preferably filled with a thermite mixture 13 which is preferably dormant until ignited or triggered. The thermite mixture 13 is preferably created to heat to a temperature which, when ignited, heats the lower casing assembly 8 and the cast iron dome or cap 9 sufficiently to heat and lower the viscosity of the asphalt 3 and/or boil the asphalt blocking the borehole 5 without compromising the lower casing assembly 8 or the iron dome or cap 9. The firing head 14 is located on the top of the dome or cap 10, and in one embodiment is preferably constructed so as to be activated when an actuation drop bar or ball 17 strikes the firing head 14 surface. An ignitable drop bar 15 is located inside the interior chamber 12. When the firing head 14 is activated the drop bar 15 ignites and drops into the thermite mixture 13 igniting the thermite mixture 13 as it proceeds (FIG. 3). Located preferably adjacent to and supporting the firing head 14 are the funnels 16, which are preferably, but not necessarily composed of aluminum or another similar material. The funnels 16 are preferably designed to allow for an actuation drop bar 17, typically from the earth's surface, to proceed down the borehole 5 and strike the firing head 14, which in turn ignites and drops the bar 15 down through the thermite mixture 13.

FIG. 3 illustrates a side, elevated view of a borehole of one embodiment of the apparatus with a thermite mixture encapsulated in a cast iron capped segment of casing in an active mode with the firing head just having been fired. The firing head 14 is activated by an actuating drop bar 17 moving through the borehole 5 and striking the firing head 14. The actuating drop bar 17 need be of a significant weight and density to allow for the actuating drop bar 17 to move through the borehole 5 without becoming stuck. The actuating drop bar 17 also need not be bar shaped and can be shaped in any form such that the actuating drop bar 17 can move through the borehole without becoming stuck. Such shapes can include, but are not limited to, a sphere, a cylinder, an ovoid, or any other shape. Once the thermite mixture 13 is ignited it begins to heat up, causing the cap or dome 9, the cap or dome 10 and the lower casing segment 8 to heat. Since the asphalt layer 3 is both thermoplastic and viscoelastic upon heating, when the lower casing segment 8 and the cap or dome 9 heat up the asphalt layer begins to soften and flow away from the lower casing segment 8 and the cap or dome 9 and the lower casing segment 8 can then be lowered and move through the asphalt layer 3 into the sand layer 4 by lowering the entire casing string having the segment 8 at its lower end.

The preferred embodiment of the invention contemplates that the column of thermite can be burned from the top of the column down to the bottom of the column, or the most preferred, from the bottom of the column upwardly to the top of the column. This variation can be achieved, for example, by varying the length of the ignition cord, or alternatively, by causing the ignitable drop bar to drop 15 to the bottom of the thermite column 13 before igniting the thermite mixture.

FIG. 4 illustrates a side, elevated view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in an active mode with an alternative ignition embodiment. In this embodiment the thermite mixture 13 is ignited when a pressure cap 18 located on the top of the dome or cap 10 is ignited. The pressure cap 18 is activated when an ignition cord 19, which typically runs to the earth's surface, is activated and sends a signal to the pressure cap 18 to actuate therein causing the pressure cap 18 to fire and ignite thermite mixture 13. It should be noted that the exhaust valve 11, located on the top of the dome or cap 10, is preferably designed to allow for any excess gas created by the thermite mixture 13 ignition to escape from the inner chamber 12 so the lower casing assembly 8 does not explode. Upon the ignition of the thermite mixture 13, the lower casing assembly 8 can move through the asphalt layer 3 as previously discussed in FIG. 3.

FIG. 5 illustrates a side, elevated view of the borehole 5 with one embodiment of a thermite mixture encapsulated in a cast iron capped segment of casing in active mode extending past the asphaltic layer 3. The lower casing unit 8 and the cap or dome 9 are superheated by the thermite mixture 13 ignition. The super heating causes the asphalt layer 3 to soften and flow so that the lower casing system 8 can then be lowered through the asphalt layer 3 and into the sand layer 4. Thus the casing is run completely through the asphalt layer 3 with no asphalt coming inside the casing.

FIG. 6 illustrates a side, elevated view of a borehole with a drill pipe and bit run through the caps 9 and 10 and any slag within the interior of the casing. Once the thermite mixture 13 has cooled significantly and the lower casing system 8 is positioned as desired in the sand layer 4 of the borehole 5, a string of drill pipe 20 and a drill bit 21 are run into the casing 8. The drill pipe 20 and bit 21 are then used to drill through the cap or dome 10, the residual thermite mixture slag 13, the dome or cap 9 and further into the sand layer 4.

FIG. 7 illustrates a side, elevated view of the borehole 8 with a cement plug and a wiper plug inside the casing. After the lower casing system 8 is drilled out by the drill pipe 20 and bit 21, a cement plug 22 as is known in the art is lowered in to the casing. It should be noted that one cement plug 22 can be used or a plurality of cement plugs 22 or wiper plugs 23 can be used. The wiper plug 23 or cement plug 22 are preferably designed to displace cement from the casing into the annulus surrounding the casing in a manner known in the art.

FIG. 8 illustrates a side, elevated view of the borehole 8 with the remaining slag and cement drilled out. After the cement is pumped and ready, it is possible to drill the remaining slag and cement 35 that is in the casing and to start drilling in the formation 4.

FIG. 9 illustrates a side, elevated view of the borehole 5 with an alternate embodiment of a thermite mixture 13 encapsulated in a capsule 26 in an active mode being ignited from the top down. In this embodiment of the invention the capsule 26 containing the thermite mixture 13 is not initially connected to the casing, but rather is lowered into the casing, for example, with a wireline, until it reaches the casing cap 31 and the area of casing that is in contact with the asphalt layer 3. In this embodiment the pressure cap 14 is attached to an ignition cord 25 which leads to and is connected internally with the top of the thermite mixture 13. In this embodiment when the pressure cap 14 is activated, for example, by a drop bar or the like, the ignition cord will ignite the thermite mixture 13 from the top of the mixture to the bottom of the mixture 13. The casing cap 31 effectively encloses the casing so that the capsule 26 will rest on the casing cap 31. When the capsule 26 is super heated by the thermite mixture, the casing cap 31 also becomes superheated, and allows the casing to pass through the asphalt as with the other embodiments.

FIG. 10 illustrates a side, elevated view of the borehole 5 with an alternate embodiment of a thermite mixture encapsulated in a capsule in an active mode being ignited from the bottom up. FIG. 10 is substantially similar to FIG. 9 except that FIG. 10 has a longer ignition cord 27 which is activated and ignited from the bottom of the cord 27 on upward. In this embodiment the thermite mixture 13 ignites from the bottom on upward. It is important to note that in FIGS. 9 and 10 the capsule 26 is actually lowered into the casing and can be easily removed, for example, by a wireline from the earth's surface, once the casing is lowered after penetrating the asphalt layer 3.

FIG. 11 illustrates a side, elevated view of a borehole with an alternate embodiment of a thermite mixture encapsulated in a capsule in an active mode positioned for extending through an asphaltic layer. In this embodiment the capsule 26 is super heated through the ignition of the thermite mixture 13. The super heating causes the asphalt layer 3 to soften and flow so that the apparatus 26 and the casing capped at the lower end can then be lowered through the asphalt layer 3 and into the sand layer 4. Thus the borehole 5 would then have casing running through the borehole 5 and passing through the asphalt layer 3 with no asphalt coming inside the casing. Not only is the casing cap 31 super heated, a lower portion of the casing 32 is super heated as well allowing for this portion of the casing 32 to pass through the asphalt layer 3 as well.

FIG. 12 illustrates the casing after the capsule 26 has been removed. After the capsule 26 has been removed from the casing the drilling can continue and the drill string 20 and bit 21 can proceed to drill to the hydrocarbon level after drilling through the end cap 31.

FIG. 13 illustrates a one type of geographic strata in which the apparatus and method according to the invention is utilized. Shown is a body of water 30 which can be a lake, river or other body of water. It is foreseen that over time silt and sediment would deposit on the rock formation 2 therein forming a silt layer 28. It is therefore foreseeable that one would have to drill through the silt layer 28 overlying a rock formation 2, overlying an asphalt formation, in order to reach the sand layer 4 and eventually the hydrocarbon layer 29. The drilling through the silt layer 28 and the rock layer 2 would be done in the normal fashion.

It may be seen from the preceding description that a new and improved system and method for heating a device for passage through subterranean asphalt has been provided. Although very specific examples have been described and disclosed, the embodiment of one form of the apparatus of the instant application is considered to comprise and is intended to comprise any equivalent structure and may be constructed in many different ways to function and operate in the general manner as explained hereinbefore. Accordingly, it is noted that the embodiment of the new and improved system and method described herein in detail for exemplary purposes is of course subject to many different variations in structure, design, application, form, embodiment and methodology. Because many varying and different embodiments may be made within the scope of the inventive concept(s) herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense. 

1. A system for allowing a casing string to be lowered through a subterranean asphalt formation, comprising: a tubular joint of casing at the lowermost end of said casing string, said tubular joint of casing having a first end and a second end, said first end having a first cap sealing said first end against entry of asphalt through said first end into the interior of said joint of casing; a second cap within the interior of said tubular joint of casing, and located between said first and second ends of said tubular joint of casing; and a thermite mixture within the interior of said tubular joint of casing, between said first and second caps, for heating the first cap and at least a portion of said tubular joint to allow said tubular joint of casing to be lowered through said asphalt formation.
 2. The system according to claim 1, including in addition thereto, a firing head for igniting the thermite mixture.
 3. The system according to claim 2, wherein said first cap comprises cast iron.
 4. The system according to claim 3, wherein said second cap comprises cast iron.
 5. The system according to claim 1, wherein said thermite resides within an envelope which can be lowered into and removed from the interior of said joint of casing by a wireline running from the earth's surface down to the envelope.
 6. An apparatus for melting through a subterranean asphalt formation comprising; a lower casing assembly with side walls, a top end, and a bottom end capable of being lowered into said asphalt formation; said bottom end being covered by a bottom cap; a top cap between said top end and said bottom end, therein creating a substantially hollow chamber within the lower casing assembly as defined by the side walls, the top cap and said bottom cap, said hollow chamber housing a thermite mixture capable of producing heat significant to reduce asphalt to a soft, viscous, flowing material upon ignition; and a firing head in contact with said top cap and with said thermite mixture, and being capable of igniting said thermite mixture, wherein when said firing head is actuated the thermite mixture ignites and produces heat which heats the bottom cap and the lower casing assembly significantly to reduce asphalt to a soft, viscous, flowing material, thereby allowing the lower casing assembly and bottom cap to be lowered through the asphalt layer.
 7. The apparatus of claim 6 further comprising: a first drop bar located in the hollow chamber and attached to the top cap, and said first drop bar being capable of igniting said thermite mixture, said firing head being in communication with the first drop bar, wherein upon actuating said firing head the first drop bar is dropped in the thermite mixture, thereby igniting the thermite mixture.
 8. The apparatus of claim 6, further comprising: a second drop bar located at the earth's surface, above the firing head, wherein when said second drop bar contacts the firing head the firing head is activated.
 9. The apparatus of claim 6, further comprising: an exhaust port for releasing gases from the hollow chamber, wherein said exhaust port runs through the top cap and into the hollow chamber.
 10. The apparatus of claim 6, further comprising: an ignition cord capable of igniting a thermite mixture, wherein said firing cap is connected to the ignition cord and said ignition cord is in contact with the thermite mixture.
 11. The apparatus of claim 10, further comprising: said ignition cord being capable of igniting said thermite mixture from the top of the thermite mixture downwardly.
 12. The apparatus of claim 10, further comprising: said ignition cord being capable of igniting said thermite mixture from the bottom of the thermite mixture upwardly.
 13. A method for lowering the bottom end of a tubular casing string through a subterranean asphalt formation, comprising the steps of: capping the said bottom end of said casing string; heating the capped bottom end and at least an additional portion of the lowermost joint of casing in said casing string, by igniting a thermite mixture located with said lowermost joint of casing; and lowering said tubular casing string through said asphalt formation during said heating step.
 14. The method according to claim 15, including in addition thereto, the step of drilling through the said capped bottom end, and then drilling further into the formations beneath the said asphalt formation. 